<tab>
    <attr-pos v='west' />
    <attr-name v="0, Tab 1" />
    <attr-name v="1, Tab 2" />
    <widget>
        <vbox>
            <label><attr-text ob='spacing' format='Tab 1 Show: Label Spacing [ %d ]' />Label 1</label>
        </vbox>
    </widget>

    <widget>
        <vbox>
            <label>
                <attr-text ob='spacing' format='Tab 2 Show: Label Spacing [ %d ]' />Label 1
            </label>
        </vbox>
    </widget>
</tab>